MPD: Support 'plchanges "-1"' to work better with MPDroid

docs/changes.rst

@@ -23,6 +23,7 @@ Another great release.
   - Split gigantic protocol implementation into eleven modules.
   - Search improvements, including support for multi-word search.
   - Fixed ``play "-1"`` and ``playid "-1"`` behaviour when playlist is empty.
+  - Support ``plchanges "-1"`` to work better with MPDroid.
 
 - Backend API:
 

mopidy/frontends/mpd/protocol/current_playlist.py

@@ -257,7 +257,7 @@ def playlistsearch(frontend, tag, needle):
     """
     raise MpdNotImplemented # TODO
 
-@handle_pattern(r'^plchanges "(?P<version>\d+)"$')
+@handle_pattern(r'^plchanges "(?P<version>-?\d+)"$')
 def plchanges(frontend, version):
     """
     *musicpd.org, current playlist section:*
@@ -268,6 +268,10 @@ def plchanges(frontend, version):
 
         To detect songs that were deleted at the end of the playlist, use
         ``playlistlength`` returned by status command.
+
+    *MPDroid:*
+
+    - Calls ``plchanges "-1"`` two times per second to get the entire playlist.
     """
     # XXX Naive implementation that returns all tracks as changed
     if int(version) < frontend.backend.current_playlist.version:

tests/frontends/mpd/current_playlist_test.py

@@ -321,6 +321,15 @@ class CurrentPlaylistHandlerTest(unittest.TestCase):
         self.assert_(u'Title: c' in result)
         self.assert_(u'OK' in result)
 
+    def test_plchanges_with_minus_one_returns_entire_playlist(self):
+        self.b.current_playlist.load(
+            [Track(name='a'), Track(name='b'), Track(name='c')])
+        result = self.h.handle_request(u'plchanges "-1"')
+        self.assert_(u'Title: a' in result)
+        self.assert_(u'Title: b' in result)
+        self.assert_(u'Title: c' in result)
+        self.assert_(u'OK' in result)
+
     def test_plchangesposid(self):
         self.b.current_playlist.load([Track(), Track(), Track()])
         result = self.h.handle_request(u'plchangesposid "0"')